502 ON THE INTERDEPENDENCE OF SCIENCE 



erysipelas is caused b}'^ a streptococcus. A host of earnest workers in different 

 countries have cultivated the new science of bacteriology, and, while opening up 

 a wide fresh domain of biology, have demonstrated in so many cases the causal 

 relation between special micro-organisms and special diseases, not only in wounds 

 but in the system generally, as to afford ample confirmation of the induction 

 which had been made by Pasteur that all infective disorders are of microbic origin. 



Not that we can look forward with anything like confidence to being able 

 ever to see the materies morhi of every disease of this nature. One of the latest 

 of such discoveries has been that by Pfeiffer of Berlin of the bacillus of influenza, 

 perhaps the most minute of all micro-organisms ever yet detected. The bacillus 

 of anthrax, the cause of a plague common among cattle in some parts of Europe, 

 and often communicated to sorters of foreign wool in this country, is a giant 

 as compared with this tiny being ; and supposing the microbe of any infectious 

 fever to be as much smaller than the influenza bacillus as this is less than that of 

 anthrax, a by no means unlikely hypothesis, it is probable that it would never 

 be visible to man. The improvements of the microscope, based on the principle 

 established by my father in the earlier part of the century, have apparently 

 nearly reached the limits of what is possible. But that such parasites are really 

 the causes of all this great class of diseases can no longer be doubted. 



The first rational step towards the prevention or cure of disease is to know 

 its cause ; and it is impossible to overestimate the practical value of researches 

 such as those to which I am now referring. Among their many achievements 

 is what may be fairly regarded as the most important discovery ever made in 

 pathology, because it revealed the true nature of the disease which causes more 

 sickness and death in the human race than any other. It was made by Robert 

 Koch, who greatly distinguished himself, when a practitioner in an obscure 

 town in Germany, by the remarkable combination of experimental acuteness 

 and skill, chemical and optical knowledge and successful micro-photography, 

 which he brought to bear upon the elucidation of infective diseases of wounds in 

 the lower animals ; in recognition of which service the enlightened Prussian 

 Government at once appointed him to an official position of great importance 

 in Berlin. There he conducted various important researches ; and at the 

 London Congress in 1881 he showed to us for the first time the bacillus of tubercle. 

 Wonderful light was thrown by this discovery upon a great group of diseases 

 which had before been rather guessed than known to be of allied nature ; 

 a precision and efficacy never before possible was introduced into their 

 surgical treatment, while the ph37sician became guided by new and sure light 

 as regards their diagnosis and prevention. 



At that same London Congress Koch demonstrated to us his ' plate culture ' 



